In the related art, in an automobile, when an automobile, a bicycle, a person, an animal, or the like (hereinafter, called a detection target) approaching in each of various directions to an own travelling vehicle is detected with a variety of sensors mounted on the vehicle and the detection target is approaching in an abnormal manner, warning of danger information is provided to a driver in various ways. As an example of the ways, it has been known that, when danger to the own vehicle is predicted, warning is provided to the driver with vibration caused by a vibration device mounted at an interior component in the own vehicle.
As producing warning with vibration, there has been known a vehicle-use seat-combined warning system, including a vibrating generator arranged at each of the center, right, and left of a driver seat of an automobile, configured to drive a pair of the vibration generators at the right and left of a seat cushion when an obstacle is detected in the lateral direction in front of the own vehicle and to drive the vibration generator at a backrest and the right-left pair of vibration generators in combination when an obstacle is detected in the lateral direction behind the own vehicle (e.g., see Patent Literature 1).
Further, there has been known a dangerous situation warning device, including a vibration generator arranged at each of two interior components distanced from each other in an automobile, configured to cause vibration to shift from one vibration generator to the other vibration generator (e.g., see Patent Literature 2).